Highly Sensitive Photoelectrochemical Biosensor Based on Quantum Dots Sensitizing Bi₂Te₃ Nanosheets and DNA-Amplifying Strategies

In this work, Bi₂Te₃ nanosheets treated with N-vinyl-pyrrolidinone showed highly sufficient and stable photocurrent for being used as a novel photoactive material. Accordingly, with CdTe quantum dots (QDs) sensitizing Bi₂Te₃ nanosheets, photoelectrochemical (PEC) biosensor coupling of DNA-amplifying strategies was constructed for sensitive miRNA-21 detection. Initially, the Bi₂Te₃ nanosheets on the electrode have conductive surface states with dissipationless electronic property, thus providing a highly stable photocurrent and a large surface-to-volume ratio. Then, with the participation of target miRNA-21 and auxiliary DNA, strand displacement amplification took place, thereby opening substantial DNA hairpins for triggering the next hybridization chain reaction (HCR). Through the HCR, long DNA tails decorated with CdTe QDs could thus be assembled on the electrode for enhancing the photocurrent of Bi₂Te₃ nanosheets. As a result, the proposed PEC biosensor showed a wide detection range from 10 fM to 100 pM with a detection limit of 3.3 fM, displaying a promising avenue to construct simple, ultrasensitive, and stable analytical techniques and tremendous potential in bioanalysis and early clinical diagnosis.